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Drive shaft question (c-4 / 9 in. rear)

3K views 17 replies 9 participants last post by  ryanv64ss 
#1 ·
I am working on a swap to add a 9 inch rear (28 spline). I have a c4 transmission. Does anyone run this combo (I assume someone must) and if so, what driveshaft modification or replacement driveshaft was needed to accomodate the larger rear end. Also, does the vehicle being lowered 1 in. factor into this?

Thanks,
Dennis
 
#3 ·
The 9" pumpkin is deeper than the 8" (the yoke will be further towards the front of the car.) I've heard of people just using their stock driveshaft w/o modification, but its not recommended. You don't want to bend the driveshaft or break the tailhousing.
Measure to be sure, but if clearance isn't within spec, then you're asking for trouble unless the situation is addressed.
You might be able to find a driveshaft from a factory 9" Cougar with the appropriate transmission, but the usual solutions are having the original driveshaft shortened or using a shorter pinion yoke, such as from a Seventies vintage 1/2 ton pickup.
 
#13 ·
I did the same thing. Went to a wrecking yard and found a 9" yoke that was about 1 1/2" shorter. Also had to buy (after much digging) a '69 Camaro 307 / Powerglide U joint yoke to adapt from the small block drive shaft to the larger u joint cap size on the 9" short yoke.
 
#11 ·
I thought cats had 2 piece drivelines, :confused: At least mine does........
I would think you would want to get rid of it if you are upgrading to a 9"
 
#12 ·
Mine had a two piece shaft too. I was going to shorten it when my driveshaft guy recommended just making up a new one-piece unit in the length I needed. With heavy duty u-joints, it was right around $200.

I'm gonna need another one when I eventually swap in the AOD.
 
#15 ·
It wasn't two separate pieces. But, rather, one piece slipped inside a larger piece with a rubber seal type insulator.

Someone's gotta have a picture anyway.
 
#17 ·
The trans yoke was a slip fit. The smaller tube inside the larger tube on the driveshaft was at the rearend end. That didn't slide.

Everything about it looked just like a traditional driveshaft. Only the tail end of the driveshaft was a slightly smaller diameter.
 
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